Some of the systems shown in this sketch are intrinsically powered (via decay heat steam) and don’t need diesel backup. These are the emergency systems. All of them can function without the large primary heat exchangers by the sea. (The ones seen in overhead photos of tsunami wreckage). Even if the primary exchangers and diesels were 100 feet under water, the emergency systems were designed to work.

The question is: Why did the emergency systems break down? What part of the emergency system was not intrinsically powered by reactor decay heat steam?

The low voltage DC for the pipe valve solenoids.

This is my opinion, agree, disagree but do not simply believe or disbelieve. Please. System design is not a religion.

The fatal design assumption was that 8 hours was enough time, it wasn’t it took more than 70 hours, the disaster ensured in sequence according to the unintended and incredibly stupid timer made effective by the run down and destruction of batteries.

Americana in a quake and tsunami zone. The written record of this goes back to at least the 1700s.

And who says the assumption of 1960s suburbia, that you can fix things quickly, will apply in the USA tomorrow?

The NRC have ordered a patch to be put in place. It took until March 2012 for the NRC to issue the order. Longer term upgrades are in train. The assumption at the heart of the technical disaster is reflective of similar assumptions involved in the siting disaster. None should be anywhere. In my opinion.